Material for organic electroluminescent devices and organic electroluminescent devices made by using the same

ABSTRACT

A material for electroluminescent devices which comprises a compound in which a heterocyclic group having nitrogen is bonded to carbazolyl group and an organic electroluminescent device having at least one organic thin film layer which is sandwiched between the cathode and the anode and contains the above material in at least one layer, are provided. The material can provide organic electroluminescent devices emitting bluish light with a high purity of color. The organic electroluminescence device uses the material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.10/504,477, filed Aug. 12, 2004 now U.S. Pat. No. 7,990,046, which is aNational Stage entry of International Application No. PCT/JP03/02995,filed Mar. 13, 2003, designating the U.S., which claims the benefit ofJapanese Application No. 2002-071398, filed Mar. 15, 2002.

TECHNICAL FIELD

The present invention relates to a material for organicelectroluminescent devices (organic EL devices) and organic EL devicesmade by using the material and, more particularly, to organic EL devicesemitting bluish light with a high purity of color.

BACKGROUND ART

Organic EL devices which utilize organic substances are expected to beuseful for application as an inexpensive full color display device ofthe solid light emission type having a great size, and variousdevelopments on the organic EL devices are being conducted. In general,an organic EL device has a construction comprising a pair of facingelectrodes and a light emitting layer sandwiched between the electrodes.

The light emission of the organic EL device is a phenomenon in which,when an electric field is applied across the two electrodes, electronsare injected from the cathode side and holes are injected from the anodeside, the electrons recombine with the holes in the light emitting layerto induce an excited state, and then, when the excited state returns tothe original state, it emits energy as light.

As the light emitting material, chelate complexes such astris(8-quinolinolato)aluminum, coumarine derivatives,tetraphenylbutadiene derivatives, bisstyrylarylene derivatives andoxadiazole derivatives are known. It has been reported that these lightemitting materials emit light in the visible region of blue to red, andit is expected that color display elements can be obtained by usingthese light emitting materials (see, for example, Japanese PatentApplication Laid-Open Nos. Heisei 8 (1996)-239655, Heisei 7(1995)-138561 and Heisei 3 (1991)-200889).

Although the practical use of displays using organic EL devices recentlystarted, the full color display device is still under development. Inparticular, an organic EL device which emits bluish light with excellentpurity of color and great efficiency of light emission has been desired.

To overcome the above problems, for example, a device in which aphenylanthracene derivative is used as the material emitting blue lightis disclosed in Japanese Patent Application Laid-Open No. Heisei 8(1996)-12600. The phenylanthracene derivative is used as the materialemitting blue light and, in general, used as a laminate of a layer ofthe material emitting blue light with a layer of a complex oftris(8-quinolinolato)aluminum (Alq). However, the efficiency of lightemission, the life and the purity of blue light are insufficient for thepractical application. Japanese Patent Application Laid-Open No.2001-160489 discloses a device in which an azafluoranthene compound isadded to the light emitting layer. However, this device emits yellow togreen light and cannot emit blue light having a sufficiently high purityof color.

SUMMARY OF THE INVENTION

The present invention has been made to overcome the above problems andhas an object of providing a material for organic EL devices which emitsbluish light with a high purity of light and an organic EL deviceutilizing the material.

As the result of intensive studies by the present inventors to achievethe above object, it was found that an organic EL device emitting bluishlight with a high purity of light could be obtained by using a compoundin which a heterocyclic group having nitrogen was bonded to carbazolylgroup as the host material. The present invention has been completedbased on this knowledge.

The present invention provides a material for organic EL devices whichcomprises a compound represented by following general formula (1):(Cz-)_(n)M_(m)  (1)wherein Cz represents a substituted or unsubstituted carbazolyl group, Mrepresents a substituted or unsubstituted heteroaromatic cyclic grouphaving 2 to 40 carbon atoms and nitrogen atom, n and m each represent aninteger of 1 to 3, a plurality of Cz may represent different groups whenn represents 2 or 3, a plurality of M may represent different groupswhen m represents 2 or 3, and M does not represent triazine group when nrepresents 3 and m represents 1.

The present invention also provides an organic EL device which comprisesa cathode, an anode and an organic thin film layer comprising at leastone layer and sandwiched between the cathode and the anode, wherein atleast one layer in the organic thin film layer contains a material fororganic EL devices described above. In the organic thin film layer, alight emitting layer, an electron transporting layer or a holetransporting layer may contain the above material for organic ELdevices.

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The material for organic EL devices of the present invention comprises acompound represented by the following general formula (1):(Cz-)_(n)M_(m)  (1)

Cz represents a substituted or unsubstituted carbazolyl group, Mrepresents a substituted or unsubstituted heteroaromatic cyclic grouphaving 2 to 40 carbon atoms and nitrogen atom, n and m each represent aninteger of 1 to 3, a plurality of Cz may represent different groups whenn represents 2 or 3, a plurality of M may represent different groupswhen m represents 2 or 3, and M does not represent triazine group when nrepresents 3 and m represents 1.

Examples of the heteroaromatic cyclic group having nitrogen representedby M include groups derived from pyridine, pyrimidine, pyrazine,triazine, aziridine, azaindolidine, indolidine, imidazole, indole,isoindole, indazole, purine, pteridine, β-carboline, naphthylidine,quinoxaline, quinazoline, phenothiazine, acridine, phenanthroline andphenazine.

Examples of the substituent to the groups represented by Cz or M ingeneral formula (1) include halogen atoms such as chlorine atom, bromineatom and fluorine atom; carbazole group, hydroxyl group, substituted orunsubstituted amine groups, nitro group, cyano group, silyl group,trifluoromethyl group, carbonyl group, carboxyl group, substituted orunsubstituted alkyl groups, substituted or unsubstituted alkenyl groups,substituted or unsubstituted arylalkyl groups, substituted orunsubstituted aromatic groups, substituted or unsubstitutedheteroaromatic heterocyclic groups, substituted or unsubstituted aralkylgroups, substituted or unsubstituted aryloxy groups and substituted orunsubstituted alkyloxyl groups. Among these groups, fluorine atom,phenyl group, naphthyl group, pyridyl group, pyrazyl group, pyrimidylgroup, cyano group, substituted or unsubstituted alkyl groups andsubstituted or unsubstituted aralkyl groups are preferable.

It is preferable that the compound represented by general formula (1)used in the present invention is a compound represented by any one ofthe following general formulae (2) to (10).

Specific examples of the compound represented by general formula (1)used in the present invention are shown in the following. However, thecompound is not limited to the compounds shown in the following.

It is preferable that the singlet energy gap of the compound representedby general formula (1) of the present invention is 2.8 to 3.8 eV andmore preferably 2.9 to 3.6 eV.

The organic EL device of the present invention comprises an anode, acathode and an organic thin film layer comprising at least one layersandwiched between the anode and the cathode, wherein at least one layerin the organic thin film layer contains the material for organic ELdevices comprising the compound represented by the above general formula(1). It is preferable that the light emitting layer in the organic ELdevice of the present invention contains the material for organic ELdevices comprising the compound represented by the above general formula(1).

The organic EL device of the present invention emits bluish light, andthe purity of color of the emitted light is as excellent as (0.12, 0.11)to (0.16, 0.19). This property is exhibited since the material fororganic EL devices comprising the compound represented by generalformula (1) of the present invention has a great energy gap.

It is preferable that the organic EL device of the present inventionemits light by a multiplet excitation which is the excitation to thetriplet state or higher.

It is preferable that the material for organic EL devices is a hostmaterial of the organic EL device. The host material is a material intowhich holes and electrons can be injected and which has the function oftransporting holes and electrons and emitting fluorescent light byrecombination of holes and electrons.

The compound represented by general formula (1) in the present inventionis useful also as the organic host material for phosphorescence devicessince the singlet energy gap is as high as 2.8 to 3.8 eV and the tripletenergy gap is as high as 2.5 to 3.3 eV.

The phosphorescence device is an organic device which comprises asubstance emitting light based on the transition from the energy levelin the triplet state to the energy level in the ground singlet statewith a stronger intensity than those emitted from other substances,examples of which include phosphorescent substances such asorganometallic complexes containing at least one metal selected fromGroups 7 to 11 of the Periodic Table, and emits light under an electricfield utilizing the so-called phosphorescence.

In the light emitting layer of the organic EL device, in general, thesinglet exciton and the triplet exciton are contained in the formedexcited molecules as a mixture, and it is reported that the tripletexciton is formed in a greater amount such that the ratio of the amountof the singlet exciton to the amount of the triplet exciton is 1:3. Inconventional organic EL devices using the phosphorescence, the excitoncontributing to the light emission is the singlet exciton, and thetriplet exciton does not emit light. Therefore, the triplet exciton isultimately consumed as heat, and the light is emitted by the singletexciton which is formed in a smaller amount. Therefore, in these organicEL devices, the energy transferred to the triplet exciton causes a greatloss in the energy generated by the recombination of holes andelectrons.

In contrast, it is considered that, by using the material of the presentinvention for the phosphorescence device, the efficiency of lightemission three times as great as that of a device using fluorescence canbe obtained since the triplet exciton can be used for the emission oflight. It is also considered that, when the compound of the presentinvention is used for the light emitting layer of the phosphorescencedevice, an excited triplet level in an energy state higher than theexcited triplet level of a phosphorescent organometallic complexcomprising a metal selected from the Group 7 to 11 of the Periodic Tablecontained in the layer, is achieved; the film having a more stable formis provided; the glass transition temperature is higher (Tg: 80 to 160°C.); holes and/or electrons are efficiently transported; the compound iselectrochemically and chemically stable; and the formation of impuritieswhich may work as a trap or cause loss in the light emission issuppressed during the preparation and the use.

The hole transporting layer, the electron injecting layer or the holebarrier layer may contain the material of the present invention. Aphosphorescent light emitting compound and the material of the presentinvention may be mixed and used in combination.

The organic EL device of the present invention comprises a cathode, ananode and an organic thin film layer comprising at least one layer andsandwiched between the cathode and the anode. When the organic thin filmlayer comprises a single layer, a light emitting layer is formed betweenthe anode and the cathode. The light emitting layer contains a lightemitting material and may further contain a hole injecting material fortransporting holes injected from the anode to the light emittingmaterial or an electron injecting material for transporting electronsinjected from the cathode to the light emitting material. It ispreferable that the light emitting material exhibits a very excellentquantum efficiency of fluorescence, has a great ability of transportingboth holes and electrons and forms a uniform thin layer. Examples of theorganic EL device of the multi-layer type include organic EL devicescomprising a laminate having a multi-layer construction such as (theanode/the hole injecting layer/the light emitting layer/the cathode),(the anode/the light emitting layer/the electron injecting layer/thecathode) and (the anode/the hole injecting layer/the light emittinglayer/the electron injecting layer/the cathode).

For the light emitting layer, in addition to the material of the presentinvention comprising the compound represented by general formula (1) ofthe present invention, conventional host materials, light emittingmaterials, doping materials, hole injecting materials and electroninjecting materials and combinations of these materials may be used incombination, where necessary. By using a multi-layer structure for theorganic EL device, decreases in the luminance and the life due toquenching can be prevented, and the luminance of emitted light and theefficiency of light emission can be improved with other dopingmaterials. By using other doping materials contributing to the lightemission of the phosphorescence in combination, the luminance of emittedlight and the efficiency of light emission can be improved in comparisonwith those of conventional devices.

In the organic EL device of the present invention, the hole injectinglayer, the light emitting layer and the electron injecting layer mayeach have a multi-layer structure. When the hole injecting layer has amulti-layer structure, the layer into which holes are injected from theelectrode is called as a hole injecting layer, and the layer whichreceives holes from the hole injecting layer and transports holes to thelight emitting layer is called as a hole transporting layer. Similarly,when the electron injecting layer has a multi-layer structure, the layerinto which electron are injected from the electrode is called as anelectron injecting layer, and the layer which receives electrons fromthe electron injecting layer and transports electrons to the lightemitting layer is called as an electron transporting layer. The layersare selected in accordance with the energy levels of the material, heatresistance and adhesion with the organic thin film layers or the metalelectrodes.

In the organic EL device of the present invention, the electrontransporting layer and the hole transporting layer may contain thematerial for organic EL devices of the present invention which comprisesthe compound represented by general formula (1).

Examples of the light emitting material and the host material which canbe used for the organic thin film layer in combination with the compoundrepresented by general formula (1) include anthracene, naphthalene,phenanthrene, pyrene, tetracene, coronene, chrysene, fluoresceine,perylene, phthaloperylene, naphthaloperylene, perynone, phthaloperynone,naphthaloperynone, diphenylbutadiene, tetraphenyl-butadiene, coumarine,oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine,cyclopentadiene, metal complexes of quinoline, metal complexes ofaminoquinoline, metal complexes of benzoquinoline, imines,diphenyl-ethylene, vinylanthracene, diaminoanthracene, diaminocarbazole,pyrane, thiopyrane, polymethine, melocyanine, oxinoid compounds chelatedwith imidazole, quinacridone, rubrene, stilbene-based derivatives andfluorescent pigments. However, the light emitting material and the hostmaterial are not limited to the compounds described above.

As the light emitting material, phosphorescent organometallic complexesare preferable since the external quantum efficiency of the device canbe improved. Examples of the metal in the phosphorescent organometalliccomplex include ruthenium, rhodium, palladium, silver, rhenium, osmium,iridium, platinum and gold. It is preferable that the organometalliccomplex is an organometallic compound represented by the followinggeneral formula (A):

In the above general formula, A¹ represents a substituted orunsubstituted aromatic hydrocarbon cyclic group or aromatic heterocyclicgroup, which is preferably phenyl group, biphenyl group, naphthyl group,anthryl group, thienyl group, pyridyl group, quinolyl group orisoquinolyl group. Examples of the substituent include halogen atomssuch as fluorine atom; alkyl groups having 1 to 30 carbon atoms such asmethyl group and ethyl group; alkenyl groups such as vinyl group;alkoxycarbonyl groups having 1 to 30 carbon atoms such asmethoxycarbonyl group and ethoxycarbonyl group; alkoxyl groups having 1to 30 carbon atoms such as methoxyl group and ethoxyl group; aryloxylgroups such as phenoxyl group and benzyloxyl group; dialkylamino groupssuch as dimethylamino group and diethylamino group; acyl groups such asacetyl group; haloalkyl groups such as trifluoromethyl group; and cyanogroup.

A² represents a substituted or unsubstituted aromatic heterocyclic grouphaving nitrogen atom as the atom forming the heterocyclic ring, which ispreferably pyridyl group, pyrimidyl group, pyrazine group, triazinegroup, benzothiazole group, benzoxazole group, benzimidazole group,quinolyl group, isoquinolyl group, quinoxaline group or phenanthridinegroup. Examples of the substituent include the substituents described asthe examples of the substituent for the group represented by A¹.

The ring having the group represented by A¹ and the ring having thegroup represented by A² may form one condensed ring. Examples of thecondensed ring include 7,8-benzoquinoline group.

Q represents a metal selected from metals of Groups 7 to 11 of thePeriodic Table, which is preferably ruthenium, rhodium, palladium,silver, rhenium, osmium, iridium, platinum or gold.

L represents a bidentate ligand, which is preferably selected fromligands of the 6-diketone type such as acetylacetonates and pyromelliticacid.

m and n each represent an integer. When Q represents a divalent metal,n=2 and m=0. When Q represents a trivalent metal, n=3 and m=0 or n=2 andm=1.

Specific examples of the organometallic complex represented by the abovegeneral formula (A) are shown in the following. However, theorganometallic complex is not limited to these compounds.

As the hole injecting material, compounds which have the ability totransport holes, exhibit the excellent effect of receiving holesinjected from the anode and the excellent effect of injecting holes tothe light emitting layer or the light emitting material, preventtransfer of excitons formed in the light emitting layer to the electroninjecting layer or the electron injecting material and have theexcellent ability of forming a thin film, are preferable. Examples ofthe hole injecting compound include phthalocyanine derivatives,naphthalocyanine derivatives, porphyrin derivatives, oxazoles,oxadiazoles, triazoles, imidazoles, imidazolones, imidazolethiones,pyrazolines, pyrazolones, tetrahydroimidazoles, oxazoles, oxadiazoles,hydrazones, acylhydrazones, polyarylalkanes, stilbene, butadiene,triphenylamine of the benzidine type, triphenylamine of the styrylaminetype, triphenylamine of the diamine type, derivatives of the abovecompounds and macromolecular materials such as polyvinylcarbazoles,polysilanes and electrically conductive macromolecules. However, thehole injecting material is not limited to these materials.

Among these hole injecting materials, the more effective hole injectingmaterials are aromatic tertiary amine derivatives and phthalocyaninederivatives. Examples of the aromatic tertiary amine derivative includetriphenylamine, tritolylamine, tolyldiphenylamine,N,N′-diphenyl-N,N′-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, N,N,N′,N′-(4-methylphenyl)-1,1′-phenyl-4,4′-diamine,N,N,N′,N′-(4-methyl-phenyl)-1,1′-biphenyl-4,4′-diamine,N,N′-diphenyl-N,N′-dinaphthyl-1,1′-biphenyl-4,4′-diamine,N,N′-(methylphenyl)-N,N′-(4-n-butylphenyl)-phenanthrene-9,10-diamine,N,N-bis(4-di-4-tolylaminophenyl)-4-phenyl-cyclohexane and oligomers andpolymers having the skeleton structure of these aromatic tertiaryamines. However, the aromatic tertiary amine is not limited to thesecompounds. Examples of the phthalocyanine (Pc) derivative includephthalocyanine derivatives and naphthalocyanine derivatives such asH₂Pc, CuPc, CoPc, NiPc, ZnPc, PdPc, FePc, MnPc, ClAlPc, ClGaPc, ClInPc,ClSnPc, Cl₂SiPc, (HO)AlPc, (HO)GaPc, VOPc, TiOPc, MoOPc and GaPc-O-GaPc.However the phthalocyanine derivative is not limited to these compounds.

As the electron injecting material, compounds which have the ability totransport electrons, exhibit the excellent effect of receiving electronsinjected from the anode and the excellent effect of injecting electronsto the light emitting layer or the light emitting material, preventtransfer of excitons formed in the light emitting layer to the holeinjecting layer and have the excellent ability of forming a thin film,are preferable. Examples of the electron injecting compound includefluorenone, anthraquinodimethane, diphenoquinone, thiopyrane dioxide,oxazoles, oxadiazoles, triazoles, imidazoles, perylenetetracarboxylicacid, quinoxaline, fluorenylidenemethane, anthraquinodimethane, anthroneand derivatives of these compounds. However, the electron injectingmaterial is not limited to these compounds.

Among these electron injecting materials, the more effective electroninjecting materials are metal complex compounds and five-memberedderivatives having nitrogen. Examples of the metal complex compoundinclude 8-hydroxyquinolinatolithium, bis(8-hydroxy-quinolinato)zinc,bis(8-hydroxyquinolinato)copper, bis(8-hydroxy-quinolinato)manganese,tris(8-hydroxyquinolinato)aluminum,tris(2-methyl-8-hydroxyquinolinato)aluminum,tris(8-hydroxyquinolinato)-gallium,bis(10-hydroxybenzo[h]quinolinato)beryllium,bis(10-hydroxy-benzo[h]quinolinato)zinc,bis(2-methyl-8-quinolinato)chlorogallium,bis(2-methyl-8-quinolinato)(o-cresolato)gallium,bis(2-methyl-8-quinolinato)-(1-naphtholato)aluminum andbis(2-methyl-8-quinolinato)(2-naphtholato)-gallium. However the electroninjecting material is not limited to these compounds.

Oxazoles, thiazoles, oxadiazoles, thiadiazoles, triazoles andderivatives of these compounds are preferable as the five-memberedderivative having nitrogen. Specific examples of the five-memberedderivative having nitrogen include 2,5-bis(1-phenyl)-1,3,4-oxazole,dimethylPOPOP, 2,5-bis(1-phenyl)-1,3,4-thiazole,2,5-bis(1-phenyl)-1,3,4-oxadiazole,2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,5-oxadiazole,2,5-bis(1-naphthyl) 1,3,4-oxadiazole,1,4-bis[2-(5-phenyloxadiazolyl)]benzene,1,4-bis[2-(5-phenyloxadiazolyl)-4-tert-butylbenzene],2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-thiadiazole,2,5-bis(1-naphthyl)-1,3,4-thiadiazole,1,4-bis[2-(5-phenylthiadiazolyl)]benzene,2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-triazole,2,5-bis(1-naphthyl)-1,3,4-triazole and1,4-bis[2-(5-phenyltriazolyl)]benzene. However, the five-memberedderivative having nitrogen is not limited to these compounds.

The property of charge injection can be improved by adding anelectron-accepting compound to the hole injecting material and by addingan electron-donating compound to the electron injecting material.

As the electrically conductive material used for the anode of theorganic EL device of the present invention, a material having a workfunction greater than 4 eV is suitable, and carbon, aluminum, vanadium,iron, cobalt, nickel, tungsten, silver, gold, platinum, palladium,alloys of these metals, metal oxides such as tin oxides and indium oxideused for ITO substrates and NESA substrates and organic electricallyconductive resins such as polythiophene and polypyrrol are used. As theelectrically conductive material used for the cathode, a material havinga work function smaller than 4 eV is suitable, and magnesium, calcium,tin, lead, titanium, yttrium, lithium, ruthenium, manganese, aluminumand alloys of these metals are used. However, the electricallyconductive material used for the cathode is not limited to thesematerials. Typical examples of the alloy include magnesium/silver,magnesium/indium and lithium/aluminum. However, the alloy is not limitedto these alloys. The composition of the alloy is controlled by thetemperature of the source of vaporization, the atmosphere and the degreeof vacuum and a suitable composition is selected. The anode and thecathode may be formed with a structure having two or more layers, wherenecessary.

The organic EL device of the present invention may comprise an inorganiccompound layer between at least one of the electrodes and the aboveorganic thin film layer. Examples of the inorganic compound used for theinorganic compound layer include various types of oxides, nitrides andoxide nitrides such as alkali metal oxides, alkaline earth metal oxides,rare earth oxides, alkali metal halides, alkaline earth metal halides,rare earth halides, SiO_(x), AlO_(x), SiN_(X), SiON, AlON, GeO_(x),LiO_(X), LiON, TiO_(X), TiON, TaO_(x), TaON, TaN_(x) and C. Inparticular, as the component contacting the anode, SiO_(x), AlO_(x),SiN_(X), SiON, AlON, GeO_(x) and C are preferable since a stableinterface layer of injection is formed. As the component contacting thecathode, LiF, MgF₂, CaF₂, MgF₂ and NaF are preferable.

In the organic EL device of the present invention, it is preferable thatat least one surface is sufficiently transparent in the region of thewavelength of the light emitted by the device so that the light emissionis achieved efficiently. It is preferable that the substrate is alsotransparent.

For the transparent electrode, the conditions in the vapor deposition orthe sputtering are set so that the prescribed transparency is surelyobtained using the above electrically conductive material. It ispreferable that the electrode of the light emitting surface has atransmittance of light of 10% or greater. The substrate is notparticularly limited as long as the substrate has the mechanical andthermal strength and is transparent. Examples of the substrate includeglass substrates and transparent films of resins. Examples of thetransparent film of a resin include films of polyethylene,ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers,polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride,polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketones,polysulfones, polyether sulfones, tetrafluoroethylene-perfluoroalkylvinyl ether copolymers, polyvinyl fluoride, tetrafluoroethylene-ethylenecopolymers, tetrafluoroethylene-hexafluoropropylene copolymers,polychlorotrifluoroethylene, polyvinylidene fluoride, polyesters,polycarbonates, polyurethanes, polyimides, polyether imides, polyimidesand polypropylene.

In the organic EL device of the present invention, it is possible that aprotective layer is formed on the surface of the device or the entiredevice is covered with a silicone oil or a resin so that stability tothe temperature, the humidity and the atmosphere is improved.

For the formation of each layer of the organic EL device of the presentinvention, any of the dry processes of film formation such as the vacuumvapor deposition, the sputtering, the plasma plating and the ion platingand the wet processes of film formation such as the spin coating, thedipping and the flow coating, can be applied. Although the thickness ofeach film is not particularly limited, it is necessary that thethickness of the film be set at a suitable value. When the thickness isexcessively great, application of a greater voltage is necessary toobtain the same output of the light, and the efficiency of lightemission decreases. When the thickness is excessively small, pin holesare formed, and sufficient light emission cannot be obtained even whenan electric field is applied. In general, a thickness in the range of 5nm to 10 μm is suitable and a thickness in the range of 10 nm to 0.2 μmis preferable.

When the wet process of film formation is used, the material formingeach layer is dissolved or suspended in a suitable solvent such asethanol, chloroform, tetrahydrofuran and dioxane, and a thin film isformed from the obtained solution or suspension. Any of the abovesolvents can be used. For any of the layers, suitable resins andadditives may be used to improve the property for film formation and toprevent formation of pin holes in the film. Examples of the resin whichcan be used include insulating resins such as polystyrene,polycarbonates, polyarylates, polyesters, polyamides, polyurethanes,polysulfones, polymethyl methacrylate, polymethyl acrylate, celluloseand copolymer resins derived from these resins; photoconductive resinssuch as poly-N-vinylcarbazole and polysilanes; and electricallyconductive resins such as polythiophene and polypyrrol. Examples of theadditive include antioxidants, ultraviolet light absorbents andplasticizers.

As described above, by using the compound represented by general formula(1) for the organic thin film layer of the organic EL device of thepresent invention, the organic EL device emitting blue light with a highpurity of color can be obtained. This organic EL device can beadvantageously used for a photosensitive member for electronicphotograph, a planar light emitting member such as a flat panel displayof wall televisions, a back light of copiers, printers and liquidcrystal displays, a light source for instruments, a display panel, amarker lamp and an accessory.

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

The triplet energy gap and the singlet energy gap of a compound weremeasured in accordance with the following methods.

(1) Measurement of the Triplet Energy Gap

The lowest excited triplet energy level T1 was measured. Thephosphorescence spectrum of a sample was measured (a 10 μmmoles/literEPA (diethyl ether:isopentane:ethanol=5:5:2 by volume) solution; 77K; aquartz cell; FLUOROLOG 11 manufactured by SPEX Company). A tangent linewas drawn to the increasing line at the short wavelength side of thephosphorescence spectrum, and the wavelength (the end of light emission)at the intersection of the tangent line and the abscissa was obtained.The obtained wavelength was converted into the energy.

(2) Measurement of the Singlet Energy Gap

The excited singlet energy gap was measured. Using a toluene solution(10⁻⁵ moles/liter) of a sample, the absorption spectrum was obtained bya spectrometer for absorption of ultraviolet and visible lightmanufactured by HITACHI Co. Ltd. A tangent line was drawn to theincreasing line at the long wavelength side of the spectrum, and thewavelength (the end of absorption) at the intersection of the tangentline and the abscissa was obtained. The obtained wavelength wasconverted into the energy.

Synthesis Example 1 Synthesis of Compound (A2):9-(2,6-dipyridyl-pyridin-4-yl)carbazole

The route of synthesis of Compound (A2) is shown in the following.

Under the atmosphere of argon, 2,6-dipyridyl-4-bromopyridine (9.4 g, 30mmole), 3,6-diphenylcarbazole (9.6 g, 30 mmole), copper iodide (0.06 g,0.32 mmole, 1% Cu), trans-1,2-cyclohexanediamine (0.4 ml, 3.3 mmole, 10eq to Cu) and potassium phosphate (14 g, 66 mmole, 2.2 eq) weresuspended in anhydrous dioxane (30 ml), and the resultant suspension washeated under the refluxing condition for 10 hours. The reaction mixturewas filtered and washed with toluene. The filtrate was concentrated and,after purification in accordance with the column chromatography, a whitesolid substance (13.2 g, the yield: 80%) was obtained. It was confirmedin accordance with ¹H-NMR and FD-MS (the field desorption mass analysis)that the product was Compound (A2) of the object compound. The result ofthe measurement by FD-MS is shown in the following.

FD-MS calcd. for C₃₉H₂₆N₄=550; found: m/z=550 (M⁺, 100).

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

Synthesis Example 2 Synthesis of Compound (A14):2-(2,6-dipyridyl-pyridin-4-yl)-5-(9-carbazolyl)pyrimidine

The route of synthesis of Compound (A14) is shown in the following.

Under the atmosphere of argon,2-(2,6-dipyridylpyridin-4-yl)-5-bromopyrimidine (12 g, 30 mmole),carbazole (5 g, 30 mmole), copper iodide (0.06 g, 0.32 mmole, 1% Cu),trans-1,2-cyclohexanediamine (0.4 ml, 3.3 mmole, 10 eq to Cu) andpotassium phosphate (14 g, 66 mmole, 2.2 eq) were suspended in anhydrousdioxane (30 ml), and the resultant suspension was heated under therefluxing condition for 10 hours. The reaction mixture was filtered andwashed with toluene. The filtrate was concentrated and, afterpurification in accordance with the column chromatography, a white solidsubstance (10.9 g, the yield: 76%) was obtained. It was confirmed inaccordance with ¹H-NMR and FD-MS that the product was Compound (A14) ofthe object compound. The result of the measurement by FD-MS is shown inthe following.

FD-MS calcd. for C₃₁H₂₀N₆=476; found: m/z=476 (M⁺, 100).

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

Synthesis Example 3 Synthesis of Compound (A33):2,6-di(9-carbazolyl)-pyridine

The route of synthesis of Compound (A33) is shown in the following.

Under the atmosphere of argon, 2,6-dibromopyridine (2.4 g, 10 mmole),3,6-diphenylcarbazole (9.6 g, 30 mmole), copper iodide (0.06 g, 0.32mmole, 1% Cu), trans-1,2-cyclohexanediamine (0.4 ml, 3.3 mmole, 10 eq toCu) and potassium phosphate (14 g, 66 mmole, 2.2 eq) were suspended inanhydrous dioxane (30 ml), and the resultant suspension was heated underthe refluxing condition for 10 hours. The reaction mixture was filteredand washed with toluene. The filtrate was concentrated and, afterpurification in accordance with the column chromatography, a white solidsubstance (4.8 g, the yield: 67%) was obtained. It was confirmed inaccordance with ¹H-NMR and FD-MS that the product was Compound (A33) ofthe object compound. The result of the measurement by FD-MS is shown inthe following.

FD-MS calcd. for C₅₃H₃₅N₃=713; found: m/z=713 (M⁺, 100).

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

Synthesis Example 4 Synthesis of Compound (A45)

The route of synthesis of Compound (A45) is shown in the following.

2-(2,4-Diphenylpyrimidin-6-yl)-6-bromopyridine (3.2 g, 8 mmole),carbazole (1.4 g, 9 mmole), copper iodide (0.08 g, 0.4 mmole) andpotassium phosphate (3.7 g, 17 mmole) were suspended in 1,4-dioxane (16ml), and trans-1,2-cyclohexanediamine (0.5 ml, 4 mmole) was added to theresultant suspension. The obtained suspension was heated under therefluxing condition for 15 hours under the atmosphere of argon. Thereaction solution was cooled to the room temperature, and water wasadded. After extraction with methylene chloride, the obtained organiclayer was washed with water and dried with anhydrous sodium sulfate.After the organic solvent was removed by distillation under a reducedpressure, 25 ml of ethyl acetate was added. The formed crystals wereseparated by filtration and washed with ethyl acetate, and crystals (2.3g, the yield: 59%) were obtained. It was confirmed in accordance with 90MHz ¹H-NMR and FD-MS that the obtained crystals were Compound (A45) ofthe object compound. The result of the measurement by FD-MS is shown inthe following.

FD-MS calcd. for C₃₃H₂₂N₄=474; found: m/z=474 (M⁺, 100)

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

Synthesis Example 5 Synthesis of Compound (A46)

The route of synthesis of Compound (A46) is shown in the following.

2,4-Dicarbazolyl-6-chloropyrimidine (2.5 g, 6 mmole),4-carbazolyl-phenylboric acid (1.6 g, 6 mmole), copper iodide (0.08 g,0.4 mmole) and tetrakis(triphenylphosphine)palladium (0.13 g, 0.1 mmole)were suspended in 1,2-dimethoxyethane (25 ml), and a solution preparedby dissolving sodium carbonate (1.8 ml, 17 mmole) in water (8 ml) wasadded to the resultant suspension. The obtained suspension was heatedunder the refluxing condition for 9 hours and 20 minutes. After thereaction solution was cooled to the room temperature, formed crystalswere separated by filtration and washed with water, methanol and ethylacetate, successively, and crude crystals (3.7 g) were obtained. Theobtained crude crystals were purified by sublimation under a reducedpressure, and purified crystals (3.1 g, the yield: 85%) were obtained.It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MS that theobtained crystals were Compound (A46) of the object compound. The resultof the measurement by FD-MS is shown in the following.

FD-MS calcd. for C₄₆H₂₉N₅=651; found: m/z=651 (M⁺, 100).

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

Synthesis Example 6 Synthesis of Compound (A47)

The route of synthesis of Compound (A47) is shown in the following.

2-Carbazolyl-5-bromopyridine (1.9 g, 6 mmole), 4-carbazolylphenyl-boricacid (1.7 g, 6 mmole) and tetrakis(triphenylphosphine)palladium (0.14 g,0.1 mmole) were suspended in 1,2-dimethoxyethane (18 ml), and a solutionprepared by dissolving sodium carbonate (1.9 ml, 18 mmole) in water (9ml) was added to the resultant suspension. The obtained suspension washeated under the refluxing condition for 9 hours and 15 minutes. Afterthe reaction solution was cooled to the room temperature, formedcrystals were separated by filtration and washed with water, methanoland ethyl acetate, successively, and crude crystals (2.9 g) wereobtained. The formed crystals were purified by sublimation under areduced pressure, and purified crystals (2.4 g, the yield: 84%) wereobtained. It was confirmed in accordance with 90 MHz ¹H-NMR and FD-MSthat the obtained crystals were Compound (A47) of the object compound.The result of the measurement by FD-MS is shown in the following.

FD-MS calcd. for C₃₅H₂₃N₃=485; found: m/z=485 (M⁺, 100)

The singlet energy gap and the triplet energy gap of the obtainedcompound are shown in Table 1.

TABLE 1 Singlet energy Triplet energy Compound gap (eV) gap (eV)Synthesis Example 1 A2 3.2 2.7 Synthesis Example 2 A14 3.2 2.8 SynthesisExample 3 A33 3.3 2.7 Synthesis Example 4 A45 3.2 2.8 Synthesis Example5 A46 3.3 2.8 Synthesis Example 6 A47 3.4 2.8

Example 1

A glass substrate (manufactured by GEOMATEC Company) of 25 mm×75 mm×1.1mm (thickness) having an ITO transparent electrode was ultrasonicallycleaned in isopropyl alcohol for 5 minutes and then further cleaned byexposure to ozone generated by ultraviolet light for 30 minutes. Theglass substrate having the transparent electrode lines which had beencleaned was attached to a substrate holder of a vacuum vapor depositionapparatus. On the surface of the cleaned substrate at the side havingthe transparent electrode, a film ofN,N′-bis-(N,N′-diphenyl-4-aminophenyl)-N,N′-diphenyl-4,4′-diamino-1,1′-biphenyl(TPD232) having a thickness of 60 nm was formed in a manner such thatthe formed film covered the transparent electrode. The formed film ofTPD232 worked as the hole injecting layer. On the formed film of TPD232,a film of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD) having athickness of 20 nm was formed. The formed film of NPD worked as the holetransporting layer. On the formed film of NPD, a film of the aboveCompound (A2) having a thickness of 40 nm was formed by vapordeposition. At the same time, Compound (D1) shown in the following wasvapor deposited in an amount such that the ratio of the amounts byweight of Compound (A2) to Compound (D1) was 40:3. Compound (D1) is alight emitting compound having a singlet energy as low as 2.79 eV sothat blue light is emitted. The formed mixed film of Compound (A5) andCompound (D1) worked as the light emitting layer. On the film formedabove, a film of BAlq shown in the following (Me means methyl group)having a thickness of 20 nm was formed. The film of BAlq worked as theelectron injecting layer. Thereafter, Li (the source of lithium:manufactured by SAES GETTERS Company) as the reducing dopant and Alqwere binary vapor deposited, and an Alq/Li film having a thickness of 10nm was formed as the second electron injecting layer (the cathode). Onthe formed Alq/Li film, metallic aluminum was vapor deposited to form ametal cathode, and an organic EL device was prepared.

When a direct current voltage of 5.0 V was applied to the organic ELdevice prepared above, blue light was efficiently emitted at a luminanceof 150 cd/m² and an efficiency of the light emission of 6.7 cd/A. Thechromaticity coordinates were (0.15, 0.16), and the purity of color wasexcellent.

Examples 2 to 3

In accordance with the same procedures as those conducted in Example 1except that compounds shown in Table 2 were used in place of Compound(A2), organic EL devices were prepared, and the voltage of the directcurrent, the luminance of the emitted light, the efficiency of the lightemission, the color of the emitted light and the purity of color weremeasured. The results are shown in Table 2.

Comparative Example 1

In accordance with the same procedures as those conducted in Example 1except that a conventional compound BCz shown in the following was usedin place of Compound (A2), an organic EL device was prepared, and thevoltage of the direct current, the luminance of the emitted light, theefficiency of the light emission, the color of the emitted light and thepurity of color were measured. The results are shown in Table 2.

TABLE 2 Organic Luminance Efficiency host material of emitted of lightColor of of light Voltage light emission emitted Chromaticity emittinglayer (V) (cd/m²) (cd/A) light coordinates Example 1 A2 5.0 150 6.7 blue(0.15, 0.16) Example 2 A14 6.0 130 5.5 blue (0.14, 0.16) Example 3 A337.0 161 6.9 blue (0.15, 0.16) Comparative BCz 8.5 120 3.4 blue (0.14,0.16) Example 1

As shown in Table 2, in comparison with the organic EL device ofComparative Example 1 using the conventional compound BCz, the organicEL devices using the compounds of the present invention could be drivenat lower voltages and emitted blue light in greater efficiencies. Sincethe energy gap of the compounds of the present invention is great, thelight emitting molecule having a great energy gap could be mixed intothe light emitting layer and used for the light emission.

Example 4

A glass substrate of 25 mm×75 mm×1.1 mm (thickness) having an ITOtransparent electrode was ultrasonically cleaned in isopropyl alcoholfor 5 minutes and then further cleaned by exposure to ozone generated byultraviolet light for 30 minutes. The glass substrate having thetransparent electrode lines which had been cleaned was attached to asubstrate holder of a vacuum vapor deposition apparatus. On the surfaceof the cleaned substrate at the side having the transparent electrode, afilm of copper phthalocyanine (CuPc shown in the following) having athickness of 10 nm was formed in a manner such that the formed filmcovered the transparent electrode. The formed film of CuPc worked as thehole injecting layer. On the formed film of CuPc, a film of4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD shown in thefollowing) having a thickness of 30 nm was formed. The formed film ofα-NPD worked as the hole transporting layer. On the formed film ofα-NPD, a film of the above Compound (A46) as the host material having athickness of 30 nm was formed by vapor deposition, and the lightemitting layer was formed. At the same time,tris(2-phenylpyridine)iridium (Ir(ppy)₃ shown in the following) as thephosphorescent Ir metal complex dopant was added. The concentration ofIr(ppy)₃ in the light emitting layer was set at 5% by weight. This layerworked as the light emitting layer. On the film formed above, a film of(1,1′-bisphenyl)-4-olato)bis-(2-methyl-8-quinolinolato)aluminum (BAlq)having a thickness of 10 nm was formed. The BAlq film worked as the holebarrier layer. On the film formed above, a film of an aluminum complexof 8-hydroxyquinoline (Alq shown in the following) having a thickness of40 nm was formed. The Alq film worked as the electron injecting layer.Thereafter, LiF as the alkali metal halide was vapor deposited in anamount such that the formed film had a thickness of 0.2 nm, and thenaluminum was vapor deposited in an amount such that the formed film hada thickness of 150 nm. The formed Alq/Li film worked as the cathode.Thus, an organic EL device was prepared.

When the obtained device was tested by passing an electric current,green light having a luminance of 100 cd/m² was emitted with theefficiency of the light emission of 44.5 cd/A at a voltage of 5.5 V anda current density of 0.22 mA/cm². The chromaticity coordinates were(0.32, 0.61).

Example 5

In accordance with the same procedures as those conducted in Example 4except that Compound (A45) was used as the host material in the lightemitting layer in place of Compound (A46), an organic EL device wereprepared, and the voltage, the current density, the luminance of theemitted light, the efficiency of the light emission and the chromaticitywere measured. The results are shown in Table 3.

Comparative Example 2

In accordance with the same procedures as those conducted in Example 4except that a conventional compound BCz shown above was used as the hostmaterial in the light emitting layer in place of Compound (A46), anorganic EL device was prepared, and the voltage, the current density,the luminance of the emitted light, the efficiency of the light emissionand the chromaticity were measured. The results are shown in Table 3.

Comparative Example 3

In accordance with the same procedures as those conducted in Example 4except that Compound (A-10) shown in the following which is described inUnited States Patent Application Laid-Open No. 2002-0028329A1 was usedas the host material in the light emitting layer in place of Compound(A46), an organic EL device was prepared and the voltage, the currentdensity, the luminance of the emitted light, the efficiency of the lightemission and the chromaticity were measured. The results are shown inTable 3.

TABLE 3 Organic host material Triplet energy gap Singlet energy gap inlight emitting layer (eV) (eV) Example 4 A46 2.8 3.3 Example 5 A45 2.83.2 Comparative BCz 2.8 3.6 Example 2 Comparative A-10 3.1 3.7 Example 3Luminance Efficiency Current of emitted of light Chromaticity Voltagedensity light emission coordinates (V) (mA/cm²) (cd/m²) (cd/A) (x, y)Example 4 5.5 0.22 100 44.5 (0.32, 0.61) Example 5 5.7 0.23 97 41.8(0.32, 0.61) Comparative 5.4 0.31 101 32.6 (0.32, 0.61) Example 2Comparative 5.9 0.32 100 31.8 (0.32, 0.61) Example 3

As shown in Table 3, in comparison with the organic EL devices ofComparative Examples 2 and 3 using conventional compounds (BCz andA-10), the organic EL devices using the compounds of the presentinvention emitted green light in greater efficiencies. Since the energygap of the compounds of the present invention was great, the lightemitting molecules having great energy gaps could be mixed into thelight emitting layer and used for the light emission.

Example 6

A glass substrate of 25 mm×75 mm×1.1 mm (thickness) having an ITOtransparent electrode was ultrasonically cleaned in isopropyl alcoholfor 5 minutes and then further cleaned by exposure to ozone generated byultraviolet light for 30 minutes. The glass substrate having thetransparent electrode lines which had been cleaned was attached to asubstrate holder of a vacuum vapor deposition apparatus. On the surfaceof the cleaned substrate at the side having the transparent electrode, afilm of phthalocyanine copper (CuPc) having a thickness of 10 nm wasformed in a manner such that the formed film covered the transparentelectrode. The formed film of CuPc worked as the hole injecting layer.On the formed film of CuPc, a film of1,1′-bis[4-N,N-di(para-tolyl)amino-phenyl]cyclohexane (TPAC shown in thefollowing) having a thickness of 30 nm was formed. The formed film ofTPAC worked as the hole transporting layer. On the formed film of TPAC,a film of the above Compound (A46) having a thickness of 30 nm wasformed by vapor deposition, and the light emitting layer was formed. Atthe same time, Ir bis[(4,6-difluorophenyl)pyridinato-N,C²′]picolinate(FIrpic shown in the following) as the phosphorescent Ir metal complexwas added. The concentration of FIrpic in the light emitting layer wasset at 7% by weight. The formed film worked as the light emitting layer.On the film formed above, a film of the aluminum complex of8-hydroxyquinoline (Alq) having a thickness of 30 nm was formed. Thefilm of Alq worked as the electron injecting layer. Thereafter, Li asthe alkali metal halide was vapor deposited, and a film having athickness of 0.2 nm was formed. Then, aluminum was vapor deposited, anda film having a thickness of 150 nm was formed. The formed Alq/Li filmworked as the cathode. An organic EL device was prepared as describedabove.

When the obtained device was tested by passing an electric current, bluelight having a luminance of 99 cd/m² was emitted with the efficiency ofthe light emission of 22.4 cd/A at a voltage of 6.4 V and a currentdensity of 0.44 mA/cm². The chromaticity coordinates were (0.17, 0.39).

Example 7

In accordance with the same procedures as those conducted in Example 6except that Compound (A45) was used as the host material in the lightemitting layer in place of Compound (A46), an organic EL devices wasprepared, and the voltage, the current density, the luminance of theemitted light, the efficiency of the light emission, the chromaticitywere measured. The results are shown in Table 4.

Comparative Example 4

In accordance with the same procedures as those conducted in Example 6except that the above conventional compound BCz was used as the hostmaterial in the light emitting layer in place of Compound (A46), anorganic EL devices was prepared, and the voltage, the current density,the luminance of the emitted light, the efficiency of the lightemission, the chromaticity were measured. The results are shown in Table4.

Comparative Example 5

In accordance with the same procedures as those conducted in ComparativeExample 4 except that α-NPD was used for the hole transporting layer inplace of the compound (TPAC) and BAlq was used for the electroninjecting layer in place of the compound Alq, an organic EL devices wasprepared, and the voltage, the current density, the luminance of theemitted light, the efficiency of the light emission, the chromaticitywere measured. The results are shown in Table 4.

TABLE 4 Organic host material Triplet energy gap Singlet energy gap inlight emitting layer (eV) (eV) Example 6 A46 2.8 3.3 Example 7 A45 2.83.2 Comparative BCz 2.8 3.6 Example 4 Comparative BCz 2.8 3.6 Example 5Luminance Efficiency Current of emitted of light Chromaticity Voltagedensity light emission coordinates (V) (mA/cm²) (cd/m²) (cd/A) (x, y)Example 6 6.4 0.44 99 22.4 (0.17, 0.39) Example 7 6.8 0.55 99 18.2(0.17, 0.39) Comparative 7.8 1.70 98 5.80 (0.16, 0.37) Example 4Comparative 7.6 1.09 99 9.15 (0.17, 0.37) Example 5

As shown in Table 4, in comparison with the organic EL devices ofComparative Examples using the conventional compound BCz, the organic ELdevices using the compounds of the present invention could be driven atlower voltages and emitted blue light in greater efficiencies. Since theenergy gap of the compound of the present invention was great, the lightemitting molecules having great energy gaps could be mixed into thelight emitting layer and used for the light emission.

Industrial Applicability

As described above in detail, by utilizing the material for organicelectroluminescence devices comprising the compound represented bygeneral formula (1) of the present invention, the organicelectroluminescence device emitting blue light having an excellentpurity of color at a high efficiency of light emission can be obtained.Therefore, the organic electroluminescence device of the presentinvention is very useful as the light source for various electronicinstruments.

The invention claimed is:
 1. A material for organic electroluminescentdevices which comprises a compound represented by any one of followinggeneral formula (3) to (5):

wherein Cz represents a substituted or unsubstituted carbazolyl group, Mrepresents a substituted or unsubstituted heteroaromatic cyclic groupselected from the group consisting of pyridine, pyrimidine, pyrazine,triazine, aziridine, azaindolidine, indolidine, indole, isoindole,indazole, purine, pteridine, β-carboline, naphthylidine, quinoxaline,quinazoline, acridine, phenanthroline and phenazine, a plurality of Czmay represent different groups, a plurality of M may represent differentgroups, and when the compound is represented by general formula (4), Mis not triazine.
 2. The material for organic electroluminescent devicesaccording to claim 1, wherein a singlet energy gap of the compoundrepresented by general formula (3) to (5) is 2.8 to 3.8 eV.
 3. Thematerial for organic electroluminescent devices according to claim 1,wherein a triplet energy gap of the compound represented by generalformula (3) to (5) is 2.5 to 3.3 eV.
 4. An organic electroluminescentdevice which comprises a cathode, an anode and an organic thin filmlayer comprising at least one layer and sandwiched between the cathodeand the anode, wherein at least one layer in the organic thin film layercontains a material for organic electroluminescent devices described inclaim
 1. 5. An organic electroluminescent device which comprises acathode, an anode and an organic thin film layer comprising at least onelayer and sandwiched between the cathode and the anode, wherein a lightemitting layer contains a material for organic electroluminescentdevices described in claim
 1. 6. An organic electroluminescent devicewhich comprises a cathode, an anode and an organic thin film layercomprising at least one layer and sandwiched between the cathode and theanode, wherein a light emitting layer contains a material for organicelectroluminescent devices described in claim
 2. 7. An organicelectroluminescent device which comprises a cathode, an anode and anorganic thin film layer comprising at least one layer and sandwichedbetween the cathode and the anode, wherein a light emitting layercontains a material for organic electroluminescent devices described inclaim
 3. 8. An organic electroluminescent device which comprises acathode, an anode and an organic thin film layer comprising at least onelayer and sandwiched between the cathode and the anode, wherein anelectron transporting layer contains a material for organicelectroluminescent devices described in claim
 1. 9. An organicelectroluminescent device which comprises a cathode, an anode and anorganic thin film layer comprising at least one layer and sandwichedbetween the cathode and the anode, wherein a hole transporting layercontains a material for organic electroluminescent devices described inclaim
 1. 10. The organic electroluminescent device according to claim 4,wherein the material for organic electroluminescent devices is anorganic host material.
 11. The organic electroluminescent deviceaccording to claim 4, which further comprises an inorganic compoundlayer sandwiched between at least one of the electrodes and the organicthin film layer.
 12. The organic electroluminescent device according toclaim 4, which emits light by a multiplet excitation which is excitationto a triplet state or higher.
 13. The organic electroluminescent deviceaccording to claim 4, which emits bluish light.